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Schor NF. Chance juxtapositions and (un)biased methods in science: More efficient at inefficiency. Neurology 2017; 89:218-219. [PMID: 28615437 DOI: 10.1212/wnl.0000000000004126] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
Affiliation(s)
- Nina F Schor
- From the Departments of Pediatrics, Neurology, and Neuroscience, University of Rochester School of Medicine & Dentistry, Rochester, NY.
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Gulisano W, Bizzoca A, Gennarini G, Palmeri A, Puzzo D. Role of the adhesion molecule F3/Contactin in synaptic plasticity and memory. Mol Cell Neurosci 2016; 81:64-71. [PMID: 28038945 DOI: 10.1016/j.mcn.2016.12.003] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/13/2016] [Revised: 12/07/2016] [Accepted: 12/22/2016] [Indexed: 12/14/2022] Open
Abstract
Cell adhesion molecules (CAMs) have a pivotal role in building and maintaining synaptic structures during brain development participating in axonal elongation and pathfinding, glial guidance of neuronal migration, as well as myelination. CAMs expression persists in the adult brain particularly in structures undergoing postnatal neurogenesis and involved in synaptic plasticity and memory as the hippocampus. Among the neural CAMs, we have recently focused on F3/Contactin, a glycosylphosphatidyl inositol-anchored glycoprotein belonging to the immunoglobulin superfamily, involved in neuronal development, synaptic maintenance and organization of neuronal networks. Here, we discuss our recent data suggesting that F3/Contactin exerts a role in hippocampal synaptic plasticity and memory in adult and aged mice. In particular, we have studied long-term potentiation (LTP), spatial and object recognition memory, and phosphorylation of the transcription factor cAMP-Responsive-Element Binding protein (CREB) in a transgenic mouse model of F3/Contactin overexpression. We also investigated whether F3/Contactin might influence neuronal apoptosis and the production of amyloid-beta peptide (Aβ), known to be one of the main pathogenetic hallmarks of Alzheimer's disease (AD). In conclusion, a further understanding of F3/Contactin role in synaptic plasticity and memory might have interesting clinical outcomes in cognitive disorders, such as aging and AD, offering innovative therapeutic opportunities.
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Affiliation(s)
- Walter Gulisano
- Section of Physiology, Department of Biomedical and Biotechnological Sciences, University of Catania, Catania, Italy
| | - Antonella Bizzoca
- Section of Physiology, Department of Basic Medical Sciences, Neuroscience and Sensory Organs, University of Bari, Bari, Italy
| | - Gianfranco Gennarini
- Section of Physiology, Department of Basic Medical Sciences, Neuroscience and Sensory Organs, University of Bari, Bari, Italy
| | - Agostino Palmeri
- Section of Physiology, Department of Biomedical and Biotechnological Sciences, University of Catania, Catania, Italy.
| | - Daniela Puzzo
- Section of Physiology, Department of Biomedical and Biotechnological Sciences, University of Catania, Catania, Italy.
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Mitsiadis TA, Pagella P. Expression of Nerve Growth Factor (NGF), TrkA, and p75(NTR) in Developing Human Fetal Teeth. Front Physiol 2016; 7:338. [PMID: 27536251 PMCID: PMC4972002 DOI: 10.3389/fphys.2016.00338] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/13/2016] [Accepted: 07/21/2016] [Indexed: 11/25/2022] Open
Abstract
Nerve growth factor (NGF) is important for the development and the differentiation of neuronal and non-neuronal cells. NGF binds to specific low- and high-affinity cell surface receptors, respectively, p75NTR and TrkA. In the present study, we examined by immunohistochemistry the expression patterns of the NGF, p75NTR, and TrkA proteins during human fetal tooth development, in order to better understand the mode of NGF signaling action in dental tissues. The results obtained show that these molecules are expressed in a wide range of dental cells of both epithelial and mesenchymal origin during early stages of odontogenesis, as well as in nerve fibers that surround the developing tooth germs. At more advanced developmental stages, NGF and TrkA are localized in differentiated cells with secretory capacities such as preameloblasts/ameloblasts secreting enamel matrix and odontoblasts secreting dentine matrix. In contrast, p75NTR expression is absent from these secretory cells and restricted in proliferating cells of the dental epithelium. The temporospatial distribution of NGF and p75NTR in fetal human teeth is similar, but not identical, with that observed previously in the developing rodent teeth, thus indicating that the genetic information is well-conserved during evolution. The expression patterns of NGF, p75NTR, and TrkA during odontogenesis suggest regulatory roles for NGF signaling in proliferation and differentiation of epithelial and mesenchymal cells, as well as in attraction and sprouting of nerve fibers within dental tissues.
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Affiliation(s)
- Thimios A Mitsiadis
- Orofacial Development and Regeneration, Institute of Oral Biology, Center for Dentistry (ZZM), University of Zurich Zurich, Switzerland
| | - Pierfrancesco Pagella
- Orofacial Development and Regeneration, Institute of Oral Biology, Center for Dentistry (ZZM), University of Zurich Zurich, Switzerland
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Lotta LT, Conrad K, Cory-Slechta D, Schor NF. Cerebellar Purkinje cell p75 neurotrophin receptor and autistic behavior. Transl Psychiatry 2014; 4:e416. [PMID: 25072321 PMCID: PMC4119222 DOI: 10.1038/tp.2014.55] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/03/2014] [Revised: 04/24/2014] [Accepted: 05/21/2014] [Indexed: 01/19/2023] Open
Abstract
The p75 neurotrophin receptor (p75NTR) is normally expressed in cerebellar Purkinje cells throughout the lifespan. Children with autism spectrum behavior exhibit apparent cerebellar Purkinje cell loss. Cerebellar transcriptome changes seen in the murine prenatal valproate exposure model of autism include all of the proteins known to constitute the p75NTR interactome. p75NTR is a modulator of cytoplasmic and mitochondrial redox potential, and others have suggested that aberrant response to oxidant stress has a major role in the pathogenesis of autism. We have created Purkinje cell-selective p75NTR knockout mice that are the progeny of hemizygous Cre-Purkinje cell protein 2 C57Bl mice and p75NTR floxed C57Bl mice. These Cre-loxP mice exhibit complete knockout of p75NTR in ~50% of the cerebellar Purkinje cells. Relative to Cre-only mice and wild-type C57Bl mice, this results in a behavioral phenotype characterized by less allogrooming of (P<0.05; one-way analysis of variance) and socialization or fighting with (each P<0.05) other mice; less (1.2-fold) non-ambulatory exploration of their environment than wild-type (P<0.01) or Cre only (P<0.01) mice; and almost twofold more stereotyped jumping behavior than wild-type (P<0.05) or Cre (P<0.02) mice of the same strain. Wild-type mice have more complex dendritic arborization than Cre-loxP mice, with more neurites per unit area (P<0.025, Student's t-test), more perpendicular branches per unit area (P<0.025) and more short branches/long neurite (P<0.0005). Aberrant developmental regulation of expression of p75NTR in cerebellar Purkinje cells may contribute to the pathogenesis of autism.
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Affiliation(s)
- L T Lotta
- Department of Pediatrics, University of Rochester School of Medicine and Dentistry, Rochester, NY, USA
| | - K Conrad
- Department of Pediatrics, University of Rochester School of Medicine and Dentistry, Rochester, NY, USA
| | - D Cory-Slechta
- Department of Pediatrics, University of Rochester School of Medicine and Dentistry, Rochester, NY, USA
| | - N F Schor
- Department of Pediatrics, University of Rochester School of Medicine and Dentistry, Rochester, NY, USA
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Abstract
In times of fiscal austerity, the tendency is to seek instant, inexpensive gratification. In the case of biomedical research, this means the shortest path to practical clinical implementation. But fueling the translational pipeline with discovery depends critically on allowing the biomedical research community to follow their science where it takes them. Fiscal constraints carry with them the risk of squelching creativity and forfeiting the power of serendipity to provide the substrate for the translational engine in the future.
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Affiliation(s)
- Nina F Schor
- Department of Pediatrics, University of Rochester School of Medicine and Dentistry, Rochester, NY, USA.
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Chandrasekaran S, Bonchev D. A network view on Parkinson's disease. Comput Struct Biotechnol J 2013; 7:e201304004. [PMID: 24688734 PMCID: PMC3962195 DOI: 10.5936/csbj.201304004] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2013] [Revised: 06/27/2013] [Accepted: 06/30/2013] [Indexed: 12/21/2022] Open
Abstract
Network-based systems biology tools including Pathway Studio 9.0 were used to identify Parkinson's disease (PD) critical molecular players, drug targets, and underlying biological processes. Utilizing several microarray gene expression datasets, biomolecular networks such as direct interaction, shortest path, and microRNA regulatory networks were constructed and analyzed for the disease conditions. Network topology analysis of node connectivity and centrality revealed in combination with the guilt-by-association rule 17 novel genes of PD-potential interest. Seven new microRNAs (miR-132, miR-133a1, miR-181-1, miR-182, miR-218-1, miR-29a, and miR-330) related to Parkinson's disease were identified, along with more microRNA targeted genes of interest like RIMS3, SEMA6D and SYNJ1. David and IPA enrichment analysis of KEGG and canonical pathways provided valuable mechanistic information emphasizing among others the role of chemokine signaling, adherence junction, and regulation of actin cytoskeleton pathways. Several routes for possible disease initiation and neuro protection mechanisms triggered via the extra-cellular ligands such as CX3CL1, SEMA6D and IL12B were thus uncovered, and a dual regulatory system of integrated transcription factors and microRNAs mechanisms was detected.
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Affiliation(s)
- Sreedevi Chandrasekaran
- Center for the Study of Biological Complexity, Virginia Commonwealth University, United States
| | - Danail Bonchev
- Center for the Study of Biological Complexity, Virginia Commonwealth University, United States
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Abstract
Neuroblastoma is, at once, the most common and deadly extracranial solid tumor of childhood. Efforts aimed at targeting the neural characteristics of these tumors have taught us much about neural crest cell biology, apoptosis induction in the nervous system, and neurotrophin receptor signaling and intracellular processing. But neuroblastoma remains a formidable enemy to the oncologist and an enigmatic target to the neuroscientist.
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Affiliation(s)
- Nina F Schor
- Department of Pediatrics, University of Rochester School of Medicine and Dentistry, Rochester, NY 14642, USA.
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Gabapentin is neuroprotective through glutamate receptor-independent mechanisms in staurosporine-induced apoptosis of cultured rat cerebellar neurons. Transl Neurosci 2013. [DOI: 10.2478/s13380-013-0139-9] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
AbstractThe anticonvulsants that are currently available modulate the activity of neuronal receptors and ion channels, which are equally involved in apoptotic pathways. We investigated the hypothesis that gabapentin (GP), an anticonvulsant without effect on glutamate receptors acting as GABA analog, has neuroprotective properties. For comparison, we chose topiramate (TPM), which has been reported to be neuroprotective via AMPA receptors blockade. For this purpose, we used rat cerebellar granule neuron (CGN) cultures and we triggered apoptosis independent of glutamate receptors with staurosporine, a broad-spectrum protein kinase inhibitor. GP at therapeutic range concentration significantly increased cell viability in CGN cultures maintained in physiological KCl concentration and reversed apoptosis induced by staurosporine. Blockade of NMDA or AMPA receptors by MK801 or NBQX, respectively, did not alter GP neuroprotection, which was reversed instead by GABA. In contrast, protective effect of TPM on STS-treated CGN cultures was annihilated by NBQX, and not altered by MK801 or GABA. Treatments with neuroprotective concentrations of GP or TPM did not modify the expression of neuronal cell adhesion molecule or synaptophysin or the morphological aspect of neuronal endings. In summary, we report that GP is neuroprotective through glutamate-receptor independent mechanisms and without alteration of neuronal plasticity markers, which makes it a possible candidate for clinical neuroprotection trials.
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Rocha de Paula M, Gómez Ravetti M, Berretta R, Moscato P. Differences in abundances of cell-signalling proteins in blood reveal novel biomarkers for early detection of clinical Alzheimer's disease. PLoS One 2011; 6:e17481. [PMID: 21479255 PMCID: PMC3063784 DOI: 10.1371/journal.pone.0017481] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/12/2010] [Accepted: 02/06/2011] [Indexed: 01/26/2023] Open
Abstract
BACKGROUND In November 2007 a study published in Nature Medicine proposed a simple test based on the abundance of 18 proteins in blood to predict the onset of clinical symptoms of Alzheimer's Disease (AD) two to six years before these symptoms manifest. Later, another study, published in PLoS ONE, showed that only five proteins (IL-1, IL-3, EGF, TNF- and G-CSF) have overall better prediction accuracy. These classifiers are based on the abundance of 120 proteins. Such values were standardised by a Z-score transformation, which means that their values are relative to the average of all others. METHODOLOGY The original datasets from the Nature Medicine paper are further studied using methods from combinatorial optimisation and Information Theory. We expand the original dataset by also including all pair-wise differences of z-score values of the original dataset ("metafeatures"). Using an exact algorithm to solve the resulting Feature Set problem, used to tackle the feature selection problem, we found signatures that contain either only features, metafeatures or both, and evaluated their predictive performance on the independent test set. CONCLUSIONS It was possible to show that a specific pattern of cell signalling imbalance in blood plasma has valuable information to distinguish between NDC and AD samples. The obtained signatures were able to predict AD in patients that already had a Mild Cognitive Impairment (MCI) with up to 84% of sensitivity, while maintaining also a strong prediction accuracy of 90% on a independent dataset with Non Demented Controls (NDC) and AD samples. The novel biomarkers uncovered with this method now confirms ANG-2, IL-11, PDGF-BB, CCL15/MIP-1; and supports the joint measurement of other signalling proteins not previously discussed: GM-CSF, NT-3, IGFBP-2 and VEGF-B.
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Affiliation(s)
- Mateus Rocha de Paula
- Centre for Bioinformatics, Biomarker Discovery & Information-Based Medicine, The University of Newcastle, Callaghan, Australia
| | - Martín Gómez Ravetti
- Departamento de Engenharia de Produção, Universidade Federal de Minas Gerais (UFMG), Belo Horizonte, Brazil
| | - Regina Berretta
- Centre for Bioinformatics, Biomarker Discovery & Information-Based Medicine, The University of Newcastle, Callaghan, Australia
| | - Pablo Moscato
- Centre for Bioinformatics, Biomarker Discovery & Information-Based Medicine, The University of Newcastle, Callaghan, Australia
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Brennaman LH, Maness PF. NCAM in Neuropsychiatric and Neurodegenerative Disorders. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2010; 663:299-317. [DOI: 10.1007/978-1-4419-1170-4_19] [Citation(s) in RCA: 74] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
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Ingraham CA, Schor NF. Necdin and TrkA contribute to modulation by p75NTR of resistance to oxidant stress. Exp Cell Res 2009; 315:3532-42. [PMID: 19818769 DOI: 10.1016/j.yexcr.2009.10.001] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/15/2009] [Revised: 10/01/2009] [Accepted: 10/02/2009] [Indexed: 12/29/2022]
Abstract
The neurotrophin receptor p75NTR provides protection from oxidant stress induced by 6-hydroxydopamine (6-OHDA) and resultant cell death. In the absence of p75NTR, TrkA is upregulated and its signaling pathway effectors are increasingly activated. Necdin, a MAGE protein and known interactor of p75NTR and TrkA, is a potential mediator of this phenomenon. Decreased expression of necdin protein in p75NTR-deficient PC12 cells decreased TrkA expression and increased PC12 cell resistance to 6-OHDA. Inhibition of JNK phosphorylation by SP600125 also resulted in increased resistance to 6-OHDA, suggesting that TrkA signaling underlies the susceptibility of these cells to oxidant stress.
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Affiliation(s)
- Christopher A Ingraham
- Department of Pediatrics, University of Rochester Medical Center, Rochester, NY 14642, USA
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Mi Z, Rogers DA, Mirnics ZK, Schor NF. p75NTR-dependent modulation of cellular handling of reactive oxygen species. J Neurochem 2009; 110:295-306. [PMID: 19457114 DOI: 10.1111/j.1471-4159.2009.06137.x] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Abstract
Our previous studies demonstrated that p75NTR confers protection against oxidative stress-induced apoptosis upon PC12 cells; however, the mechanisms responsible for this effect are not known. The present studies reveal decreased mitochondrion membrane potential and increased generation of reactive oxygen species (ROS) in p75NTR-deficient PC12 cells as well as diminution of ROS generation after transfection of a full-length p75NTR construct into these cells. They also show that p75NTR deficiency attenuates activation of the phosphatidylinositol 3-kinase --> phospho-Akt/protein kinase B pathway in PC12 cells by oxidative stress or neurotrophic ligands and inhibition of Akt phosphorylation decreases the glutathione (GSH) content in PC12 cells. In addition, decreased de novo GSH synthesis and increased GSH consumption are observed in p75NTR-deficient cells. These findings indicate that p75NTR regulates cellular handling of ROS to effect a survival response to oxidative stress.
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Affiliation(s)
- Zhiping Mi
- Department of Pediatrics, University of Rochester, Rochester, New York 14642, USA
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New approaches to pharmacotherapy of tumors of the nervous system during childhood and adolescence. Pharmacol Ther 2009; 122:44-55. [PMID: 19318043 DOI: 10.1016/j.pharmthera.2009.01.001] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/02/2009] [Indexed: 12/20/2022]
Abstract
Tumors of the nervous system are among the most common and most chemoresistant neoplasms of childhood and adolescence. Malignant tumors of the brain collectively account for 21% of all cancers and 24% of all cancer-related deaths in this age group. Neuroblastoma, a peripheral nervous system tumor, is the most common extracranial solid tumor of childhood, and 65% of children with this tumor have only a 10 or 15% chance of living 5 years beyond the time of initial diagnosis. Novel pharmacological approaches to nervous system tumors are urgently needed. This review presents the role of and current challenges to pharmacotherapy of malignant tumors of the nervous system during childhood and adolescence and discusses novel approaches aimed at overcoming these challenges.
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Korade Z, Kenchappa RS, Mirnics K, Carter BD. NRIF is a regulator of neuronal cholesterol biosynthesis genes. J Mol Neurosci 2008; 38:152-8. [PMID: 18677445 DOI: 10.1007/s12031-008-9136-9] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/16/2008] [Accepted: 07/09/2008] [Indexed: 11/30/2022]
Abstract
Cholesterol is a critical component of neuronal membranes, required for normal signal transduction. We showed previously that adult hippocampal neurons co-express high levels of cholesterogenic enzymes, and that their expression is under the control of the p75 neurotrophin receptor (p75NTR). Most of the cellular effects of p75NTR are mediated via interacting proteins, including neurotrophin receptor interacting factor (NRIF). In this study, we tested the hypothesis that p75NTR-dependent regulation of cholesterol and lipid biosynthesis genes is mediated by NRIF. We found that in vitro down regulation of NRIF expression decreased the mRNA for two main cholesterogenic enzymes, 3-hydroxy-3-methylglutaryl-coenzyme A reductase (Hmgcr; EC 2.3.3.10) and 7-dehydrocholesterol reductase (Dhcr7; EC 1.3.1.21). Further analyses revealed that NRIF-dependent and Dhcr7-dependent transcriptional changes show a high degree of overlap, and that NRIF reduction resulted in reduced expression of sterol-sensing domain protein SCAP, followed by a decrease in mRNA levels of SRE-motif containing genes (HMGCR, FASN, SREBP2, S1P, and SQS1). Finally, a reduction in cholesterol biosynthesis-related gene expression was also observed in hippocampal tissue of mice with NRIF deletion. Our combined in vitro and in vivo studies suggest that hippocampal neuronal cholesterol biosynthesis is regulated through the p75NTR interacting factor NRIF.
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Affiliation(s)
- Zeljka Korade
- Department of Biochemistry, Vanderbilt University School of Medicine, 8124A MRB III, Nashville, TN 37232, USA.
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Parks AL, Curtis D. Presenilin diversifies its portfolio. Trends Genet 2007; 23:140-50. [PMID: 17280736 DOI: 10.1016/j.tig.2007.01.008] [Citation(s) in RCA: 128] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/12/2006] [Revised: 12/14/2006] [Accepted: 01/23/2007] [Indexed: 12/13/2022]
Abstract
Presenilin, the catalytic member of the gamma-secretase proteolytic complex, was discovered through its roles in generating Alzheimer's-disease-associated amyloid-beta peptides from the amyloid-beta precursor protein and in releasing the transcriptionally active domain of the receptor Notch. Recent work has revealed many additional cleavage substrates and interacting proteins, suggesting a diversity of roles for presenilin during development and adult life, some of which might contribute to Alzheimer's disease progression. Although many of these functions depend on the proteolytic activity of gamma-secretase, others are independent of its role as a protease. Here, we review recent data on candidate functions for presenilin and its interactors and on their potential significance in disease.
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Affiliation(s)
- Annette L Parks
- Biology Department, Boston College, Chestnut Hill, MA 02467, USA.
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Fritz MD, Mirnics ZK, Nylander KD, Schor NF. p75NTR enhances PC12 cell tumor growth by a non-receptor mechanism involving downregulation of cyclin D2. Exp Cell Res 2006; 312:3287-97. [PMID: 16887120 DOI: 10.1016/j.yexcr.2006.06.029] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/16/2006] [Revised: 06/22/2006] [Accepted: 06/22/2006] [Indexed: 01/20/2023]
Abstract
p75NTR is a member of the tumor necrosis superfamily of proteins which is variably associated with induction of apoptosis and proliferation. Cyclin D2 is one of the mediators of cellular progression through G1 phase of the cell cycle. The present study demonstrates the inverse relationship between expression of cyclin D2 and expression of p75NTR in PC12 cells. Induction of p75NTR expression in p75NTR-negative PC12 cells results in downregulation of cyclin D2; suppression of p75NTR expression with siRNA in native PC12 cells results in upregulation of cyclin D2. The effects of p75NTR on cyclin D2 expression are mimicked in p75NTR-negative cells by transfection with the intracellular domain of p75NTR. Cyclin-D2-positive PC12 cell cultures grow more slowly than cyclin-D2-negative cultures, and induction of expression of cyclin D2 slows the culture growth rate of cyclin-D2-negative cells. Finally, subcutaneous murine xenografts of cyclin-D2-negative, p75NTR-positive PC12 cells more frequently and more rapidly produce tumors than the analogous xenografts of cyclin-D2-positive, p75NTR-negative cells. These results suggest that p75NTR suppresses cyclin D2 expression in PC12 cells by a mechanism distinct from its function as a nerve growth factor receptor and that cyclin D2 expression decreases cell culture and xenografted tumor growth.
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Korade Z, Mi Z, Portugal C, Schor NF. Expression and p75 neurotrophin receptor dependence of cholesterol synthetic enzymes in adult mouse brain. Neurobiol Aging 2006; 28:1522-31. [PMID: 16887237 DOI: 10.1016/j.neurobiolaging.2006.06.026] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2006] [Revised: 06/06/2006] [Accepted: 06/22/2006] [Indexed: 11/30/2022]
Abstract
Normal brain function depends critically on cholesterol. Although cholesterol is synthesized locally in the adult brain, the precise anatomical localization of cholesterogenic enzymes is not known. Here we show that 3-hydroxy-3-methylglutaryl-coenzyme A reductase (HMG-CoAred) and 7-dehydrocholesterol reductase (7dhcred), the first and last enzymes, respectively, in the cholesterol biosynthesis pathway, are co-expressed in neurons throughout adult murine brain. Co-localization is most prominent in cortical, hippocampal, and cholinergic neurons. Since adult hippocampal and cholinergic neurons express p75 neurotrophin receptors (p75NTR) we hypothesized that p75NTR regulates expression of cholesterogenic enzymes. Treatment of Neuro2a neuroblastoma cells or primary cerebellar cultures with siRNA downregulates p75NTR and decreases the expression level of HMG-CoAred and 7dhcred. Native neuroblastoma cell lines with differential expression of p75NTR differentially express 7dhcred; 7dhcred expression correlates with p75NTR expression. This suggests that, in p75NTR-expressing cells, p75NTR regulates cholesterol synthesis through regulation of HMG-CoAred and 7dhcred expression. The unexpected localization of cholesterogenic enzymes in adult neurons suggests that at least some adult neurons retain the ability to synthesize cholesterol.
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Affiliation(s)
- Zeljka Korade
- Pediatric Center for Neuroscience, Children's Hospital of Pittsburgh, Department of Pediatrics, University of Pittsburgh, PA, United States
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Schor NF. The p75 neurotrophin receptor in human development and disease. Prog Neurobiol 2005; 77:201-14. [PMID: 16297524 DOI: 10.1016/j.pneurobio.2005.10.006] [Citation(s) in RCA: 77] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/03/2004] [Revised: 10/19/2005] [Accepted: 10/21/2005] [Indexed: 11/29/2022]
Abstract
The functional effects of nerve growth factor (NGF) and its precursor, pro-NGF, are thought to be mediated through binding of these ligands to one or both of their receptors, TrkA and p75NTR. While the signaling pathways and downstream effects of NGF binding to TrkA are reasonably well known, those related to the binding of NGF and pro-NGF to p75NTR are less well understood. Furthermore, p75NTR appears to play functional roles that are unrelated to its ability to bind NGF and pro-NGF, some of which are ligand-independent and others of which are dependent upon binding to other neurotrophins. As these functional roles and their biochemical mechanisms become better known, the importance of p75NTR, related receptors, and both extracellular ligands and intracellular interactors and effectors for human development and health has become increasingly apparent. A complete understanding of p75NTR and its cellular partners is best served by approaching the remaining questions from both sides, with studies of function in normal states and studies of dysfunction in aberrant states mutually informing one another.
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Affiliation(s)
- Nina Felice Schor
- Department of Pediatrics, University of Pittsburgh, 3705 Fifth Avenue, Pittsburgh, PA 15213, USA.
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